1. Field of the Invention
The invention relates to vertically disposed exhaust pipes as used on off-road vehicles.
2. Description of the Related Art
Vehicles having a power source such as an internal combustion engine are typically provided with an exhaust pipe that discharges exhaust fumes into the atmosphere. Many such vehicles, such as automobiles, provide exhaust pipes that are horizontally disposed beneath the vehicle, such that the operator and passers-by are hindered from touching the hot exhaust pipe. Many off-road vehicles, such as tractors, are provided with vertically disposed exhaust pipes for dispersing exhaust fumes above the head of the operator. The warm fumes rise as they exit the exhaust pipe and therefore do not cause discomfort to the operator, or damage to growing vegetation.
However, rain can accumulate in vertical exhaust pipes during periods of non-use. Rain water can flow down the inside of the pipe to the exhaust manifold within the engine, and cause difficulty in starting the engine. Also, when the engine is started, the water that has accumulated in the exhaust pipe is ejected from the pipe by the exhaust gases that are forced out of the pipe. The ejected water particles can be dirty since the rainwater in the pipe mixes with the exhaust soot that builds up within the pipe. This sooty moisture ejected from the exhaust pipe can undesirably soil or stain the operator or structures that are close to the exhaust pipe when the vehicle engine is started.
It is known to provide a flapper lid for a vertical exhaust pipe that acts to prevent rainwater from entering the pipe. Such a mechanism includes a lid hinged to the opening at the top of the exhaust pipe. The weight of such a lid keeps it closed over the exhaust pipe opening to exclude rain from entering during periods of non-use. When the engine is started the exhaust fumes flow upwardly within the pipe and press against the lid to pivot the lid to an opened position. The fumes are thereby allowed to exit the exhaust pipe. A hinged lid adds weight to the top of the pipe and raises the center of gravity of the exhaust pipe. Exhaust pipes with hinged lids may therefore require the use of stronger support structures for coupling the pipe to the vehicle in order to keep the pipe upright when used with large power sources that create a large amount of vibration, or during operation over rough terrain. Hinged lids can also be relatively costly to manufacture and attach to exhaust pipes, and may be perceived as unsightly.
Therefore, it would be desirable to provide a vertical exhaust pipe that substantially eliminates the problem of rainwater being ejected from the exhaust pipe when the engine is started. It would be desirable for such a mechanism to be provided such that the center of gravity of the exhaust pipe is not significantly raised. The support structure would therefore not need to be reinforced or strengthened when used on small vehicles. It would be desirable for such a mechanism to outwardly resemble a conventional upright exhaust pipe during normal operation. It would also be desirable for such a mechanism to be simple in construction and relatively inexpensive to manufacture and assemble.